Abstract:
Resonant optical gyroscope is very important for measuring angular velocity of rotation.Because the gyro signal is quite weak and measuring the signal of the frequency difference requires fairly stable resonant frequency, it’s crucial to track and lock the resonant frequency. The research was carried out aimed to the problem of frequency tracking and locking in this paper. The paper also made a analysis of the high-Q microsphere cavity.The technology of frequency tracking and locking was a priority for all, and this article focused on the analog frequency locking circuit. This circuit was divided into four parts:the triangle wave generating circuit, the PI controlling circuit, the additive selecting circuit and the transmission peaks controlling circuit. After modulation and demodulation, the differential frequency signal entered into the PI controlling circuit. Then it was controlled by the PI circuit and went into the adder. The triangle wave signal generated by the triangle wave generating circuit also served as the input of the adder. There was another input of the adder which was called offset signal. The transmission peak signal entered into the transmission peaks controlling circuit and through a threshold value comparator and generated a Lock-CTRL signal, the positive and negative level value of this signal was set as a determination condition which determine the choice of the adder to the three input signals, so as to realize the gear control to the frequency locking circuit.The microsphere cavity was the core component of the system. The tapered fiber-microsphere cavity coupling structure was theoretical analyzed, and the preparation of the structure was introduced. The calculated diameter of the microsphere which was used in this system was about1mm, and the value of Q can be the order of magnitude of107, the fineness of magnitude can reach103.In the end, the system which sensitive optical element was a microsphere cavity and the frequency fast-tracking and locking approach was analog locking circuit was tested on the turntable. Experiments showed that the laser frequency can be locked to the resonant frequency as soon as possible, and the process was high stability, and for a long time without losing the locking. Within a certain time, the locking finesse was higher when the turntable’s speed was less than lrad/s.